In a window display, on the busiest shopping street in London, was an insitu concrete wall. The effect is an imaginary enclosure around the window that is normally decorated for the display. What created this effect was a simple concrete patterned wallpaper! This particular example was a rough cast finish, but there are others. Enhancing the illusion, the wide format of ink jet printed wallpaper puts the joints in about the same location as the formwork would be. The effect is uncanny.